Counterflow stripping tube

ABSTRACT

Countercurrent stripping pipe for removing volatile organic constituents from reaction products, having a column pipe ( 201 ) composed of a plurality of pipe sections ( 201   a-d ), in which trays ( 202 ) are arranged, connections ( 205, 208 ) for supplying and removing the reaction products and connections ( 206, 207 ) for supplying and removing at least one stripping agent in countercurrent to the reaction products. In accordance with the invention, a plurality of successive trays ( 202 ) in each case are joined to one another and form at least two inserts ( 211   a-c ) which can be removed from the column pipe ( 201 ).

CONTINUING APPLICATION DATA

The present application is a 371 of International Application No.PCT/EP99/07639, filed on Oct. 12, 1999.

The present invention relates to a countercurrent stripping pipe forremoving volatile organic constituents from reaction products,especially from polymer solutions and polymer dispersions.

In the course of production processes in the chemical industry, productsare formed which still contain unwanted volatile organic components. Inthe case of polymerization processes, for instance, a very wide varietyof impurities may remain in the reaction product, examples beingresidual monomers resulting from incomplete conversion of the startingmaterials, saturated, unpolymerizable compounds entrained with thestarting materials, and products of low molecular mass originating fromsecondary reactions. These volatile organic constituents often have avery intense odor and in some cases may even be injurious to health.Polymer dispersions in particular, however, have found numerousapplications in which an odor nuisance is inadmissible. As typical ofsuch applications there may be mentioned interior applications, wherepolymer dispersions are employed, for example, as tile adhesives orcarpet adhesives or in film-forming resins. Odorless polymer dispersionsare also required by the paper industry, for example, in the form ofpaper coating dispersions, or in the form of pressure-sensitive adhesivedispersions. Finally, the cosmetics industry, to produce hair gels, forinstance, or the textile industry, to produce coating compositions fornonwovens, for instance, makes use of polymer dispersions which are notpermitted to have any substantial inherent odor. As a result, for manyapplications, but especially for interior applications and in thefoodstuffs or cosmetics sector, it is necessary to remove residualvolatiles from polymers as far as is possible.

For removing the volatile organic constituents from reactionproducts—for example, from polymer solutions or from aqueous polymerdispersions and suspensions prepared by free-radical polymerization ofvinyl-type monomers—deodorization processes have been developed. Inaddition to chemical processes, which usually affect only theunsaturated compounds, however, use is made predominantly of strippingprocesses, in which a stripping gas is passed through the suspension ordispersion. Stripping gases employed include air, oxygen, nitrogen,supercritical carbon dioxide, ozone, and water vapor. Also known areprocesses in which chemical deodorization is followed by a physicaldeodorization with the aid of a stripping process.

DE-C-12 48 943, for example, describes an apparatus for batchwiseremoval of odoriferous substances from aqueous polymer dispersions.Here, the dispersion is charged to a vessel and the unwanted componentsare expelled by introducing steam at the bottom of the vessel.

For larger amounts of dispersions to be treated, continuous columnprocesses are being employed increasingly.

The Applicant's International Patent Application WO 97/45184, forexample, describes a column and a process for deodorizing dispersions.Here, the dispersion is treated with steam in a countercurrent columncomprising dual-flow trays and/or cross-flow trays, the steam, with apressure of 0.1-0.7 bar, being introduced into the column incountercurrent to the dispersion. With the countercurrent columndescribed in WO 97/45184 it is possible to simplify the column trays andincrease the specific throughput. The known countercurrent columns areproduced in one piece, with the trays being subsequently screwed ontowelded-in support rings.

A construction of this kind, however, is subject to disadvantages. Sincedispersions readily form films and coagulum, frequent cleaning of thetrays is required. Since the trays are firmly screwed down in the columnand removal of the individual trays is extremely time-consuming, thestripping column has to be provided with a manhole and at least onecleaning aperture per tray. Using such a manhole, an operative is ableto clean the associated tray and the adjacent wall areas extending tothe next tray, using a high-pressure water jet. In this case it isnecessary to operate with water pressures of up to 2000 bar, which isassociated with considerable risk to a cleaning operative working withina very confined space. The provision of a manhole necessitates, inaddition, a tray spacing of at least 600 mm and a column diameter ofabout 1 m. For effective separation, this results in column heights ofmore than 20 m and an internal volume of at least 25 m³. With typicallyfrom 25 to 30 trays, this results in complex columns having a total ofmore than 100 ports, manholes and cleaning covers. These ports andcovers are potential dirt traps. The cleaning of the trays in theinstalled state, as well, proves to be complex and labor intensive.Changing the tray geometry (dual-flow trays or cross-flow trays or trayswith a different perforation pattern, for different throughputs) resultsin column downtime of several weeks.

For deodorizing relatively small batches of product, furthermore, thereis the disadvantage that comparatively small volumes of dispersion mustbe pumped through a relatively large and complex apparatus.

It is an object of the present invention to simplify the construction ofthe countercurrent column known from WO 97/45184 without detriment toits high specific throughput in order in particular to ensure greaterease of cleaning and of tray replacement. In addition, the apparatus ofthe invention should also be suitable for deodorizing relatively smallbatches of product.

We have found that this object is achieved by the countercurrentstripping pipe having the features of the present main claim.Advantageous embodiments of the invention are provided by the subclaims.

The present invention therefore provides a countercurrent stripping pipefor removing volatile organic constituents from reaction products,comprising a column pipe which is composed of a plurality of pipesections and in which trays are arranged, connections for supplying andremoving the reaction products and connections for supplying andremoving at least one stripping agent in countercurrent to the reactionproducts, a plurality of successive trays being connected to one anotherto form at least two separate inserts which can be removed from thecolumn pipe.

DE 1 519 672 and Swiss Patent CH 562 046 describe fractionating columnshaving trays connected to form removable inserts. The use of such trayinserts in countercurrent stripping pipes, however, is not disclosed bythese documents. Furthermore, said prior art proposes joining all of thetrays to form a single insert. The modular design provided in accordancewith the invention, with a plurality of inserts, is not described in theprior art.

The countercurrent stripping pipe of the invention combines numerousadvantages:

The trays of the stripping pipe can be replaced or removed from the pipewithout prolonged plant shutdown. Whereas in the case of conventionalstripping columns the individual trays must first be unscrewed fromtheir respective support rings, in the case of the stripping pipe of theinvention the complete inserts can be lifted in succession from thepipe. It is therefore possible to clean the inserts outside the pipe,which represents a safety advantage for the cleaning operatives. It isalso possible to install inserts held ready as replacements, immediatelyafter the soiled inserts have been removed. This tray changeoverrequires just a few days' shutdown of the plant, whereas with acomparable conventional countercurrent column the changeover of thefixed trays entails at least a two week downtime period.

In addition, however, this also removes the need to provide a separatemanhole and associated cleaning ports for each tray in the strippingpipe of the invention. In contrast to the known stripping columns,therefore, the stripping pipe of the invention, despite a comparablenumber of trays, is distinguished by a drastic decrease in the number ofconnection ports. Depending on the embodiment, only about 20 to 30 portswill be present, these being primarily connections for temperature orpressure monitoring means, inspection windows, or connections for takingsamples.

This simpler constructional design also facilitates the cleaning of thestripping pipe, since the reduction in the number of ports isaccompanied by the omission of many of the poorly accessible anddifficult-to-clean regions which are present on the inside ofconventional columns.

The simplified design proposed by the invention is also intended to beemphasized by the terminology used here: owing to the few externallyvisible ports, the countercurrent stripping pipe of the invention reallydoes have the character of a simple “pipe”, whereas the known strippingcolumns, with their numerous ports, covers and connections, have thetypical appearance of a tray “column”.

In accordance with the invention, the trays can be connected to forminserts in a wide variety of ways. For example, it is possible to screwthe trays to one another with the aid of threaded rods. Preferably,however, the trays are welded with the aid of metal connecting plates,which results in particularly stable inserts.

The outer periphery of the inserts may carry guide means, such asrollers or gliding elements, so that they can be lifted out of thestripping pipe with no risk of damage.

The inserts can be fixed in the stripping pipe. With particularpreference, however, they are simply placed atop of one another orplaced on or hung from suitable mountings in the pipe.

Preferably from 2 to 10 of these inserts are arranged in the columnpipe, in which case each insert will then have preferably 3 to 10 trays,more preferably from 4 to 7 trays. Particular preference here is givento 6 trays per insert. With fewer trays per insert the number of insertsrequired becomes too great, which makes tray removal more complicatedagain. A greater number of trays per insert makes the individual insertsheavier and more difficult to handle.

The diameter of the trays of an insert advantageously correspondsessentially to the internal diameter of the column pipe and ispreferably from 100 to 2500 mm, with particular preference from 500 to1600 mm. The necessary play between the outer periphery of a tray andthe inner wall of the pipe can be compensated by elastic sealing lipswhich run around the outer periphery of the tray.

The distance between successive trays in an insert can be, for example,from 200 to 1000 mm, preferably from 400 to 600 mm. An insert will thentypically have a height of between 2 and 3 meters.

In the case of relatively small embodiments of the apparatus of theinvention, the head of the column, which is widened if desired, can bedesigned so as to be removable. Alternatively, it may have an openingwhich can be closed by means of a removable cover and whose diameter issufficient to allow removal through the aperture of the inserts with theaid of a lifting tool.

The column pipe of the invention is composed of two or more pipesections. Each pipe-section is preferably assigned one insert; in otherwords, the length of the pipe section and the height of the insert arematched to one another.

In accordance with a first embodiment, the internal diameters ofsucceeding pipe sections decrease from top to bottom, the internaldiameter of a pipe section remaining essentially constant over itslength. Arranged in each pipe section, then, is an insert which can beremoved through the upper aperture of the column pipe and whose trayshave a diameter matched to the corresponding pipe section. By virtue ofthe upwardly widening stripping pipe, the individual inserts can beremoved without risk of jamming.

In this embodiment, the inserts preferably lie on steplike connectingregions between each pair of successive pipe sections, on a widenedflange piece, for instance. Alternatively, the inserts may stand on topof one another in the column pipe. This variant is preferred in the caseof relatively small columns in particular. In small and compact columnswhere the individual pipe sections can be separated from one anotherwithout problems it is also possible to clamp the individual insertsinto the flange connections between the pipe sections.

The column head can be designed as a gravity separator for foam andentrained droplets of liquid. In this case the internal diameter of thehead will be greater than that of the column pipe. In its lower region,the column may have an extension of about 1 to 4 meters in length whichconstitutes the column bottom. The deodorized reaction products arecollected in this column bottom. Normally, the column bottom serves asan initial charge for subsequent process stages.

The trays employed can be dual-flow trays and/or cross-flow trays. Traysof this kind and their design are described, for example, in KlausSattler, “Thermische Trennverfahren”, VCH 1988. Dual-flow trays areparticularly preferred here since their construction does not endow themwith any dead zones: this first reduces the expense of cleaning andsecond permits smaller column cross sections. Because of the greaterefficiency, it is also possible to reduce the number of trays and thusthe column height.

Stripping agents which can be used are preferably gaseous substancessuch as air, oxygen, nitrogen, supercritical carbon dioxide, and ozone.In the case of the countercurrent stripping pipe of the invention,however, particular preference is given to use of steam as strippingagent. The steam is preferably introduced into the column bottom by wayof one or more connection ports and is drawn off at the top of thecolumn. Each of these connection ports preferably has a pneumaticallyoperable valve with a downstream distributor means with which the steamcan be introduced into the column bottom through numerous fine orifices.

The reaction products for deodorization are fed in the upper region ofthe column pipe, preferably in the enlarged head of the column. Withparticular preference, the reaction products are introduced tangentiallyinto the column head about midway up its vertical extent. By virtue ofthis measure it is possible to achieve a drastic reduction in foaming.

The apparatus of the invention can be deployed to particular advantageto prepare polymer dispersions or polymer suspensions having a low VOCcontent (VOC=volatile organic compounds). For a detailed description ofthe preparation and deodorization of preferred dispersions which can betreated with the countercurrent stripping pipe of the invention,reference may be made to the disclosure content of the Applicant'sInternational Application WO 97/45184, which is expressly incorporatedherein by reference.

The countercurrent stripping pipe of the invention is also suitable withparticular advantage for replacing the organic solvent of a polymersolution by water.

The present invention is elucidated in more detail below with referenceto preferred embodiments depicted in the attached drawings,

wherein

FIG. 1 shows a diagram of a first countercurrent stripping pipe of theinvention suitable especially for relatively small batches of product;

FIG. 2 shows a cutaway of the stripping pipe of FIG. 1 in lengthwiseaxial section with inserts inserted therein and standing one atopanother;

FIG. 3 shows a diagram of a second stripping pipe of the inventionsuitable for large batches of product;

FIG. 4 shows a cutaway of the stripping pipe of FIG. 3 in lengthwiseaxial section with an insert lying on it;

FIG. 5 shows a detail of FIG. 4, on an enlarged scale;

FIG. 6 shows a cutaway of a stripping pipe of the invention inlengthwise axial section, in which cross-flow trays are used instead ofdual-flow trays;

FIG. 7 shows a plan view of a dual-flow tray;

FIG. 8 shows a plan view of a cross-flow tray; and

FIG. 9 shows a prior art stripping column.

Referring to FIG. 9, the design of a conventional stripping column willbe explained first of all. The known stripping column 400 consists of acolumn pipe 401 which is manufactured from one piece and in which 30trays 402 having a diameter of 1500 mm are arranged. The trays arescrewed onto support rings (not visible in the drawing) which are weldedin the column pipe 401. The stripping column 400 has a widened columntop 403 and a likewise widened column bottom 404. Top and bottom eachhave a diameter of 2300 mm. The overall height of the known strippingcolumn is 26.2 m, with a volume of 57 m³. The dispersion containingresidual volatile impurities or a solvent-based polymer solution ispassed into the column through an entry port 405 at the height of thetopmost column 402 a. At the same time, steam is blown in through aplurality of ports 406 at the column bottom 404, and this steam ascendswithin the column pipe in countercurrent to the dispersion and expelsthe residual volatiles from the dispersion. In the case of a polymersolution, the organic solvent is driven from the solution and replacedby water. Steam and residual volatiles or organic solvent leave thecolumn 400 via an exit port 407 at the column top 403, said port beingunder a slight subatmospheric pressure. Efficient mixing of thedispersion or polymer solution with the ascending steam takes place onthe trays 402. The decontaminated dispersion or polymer solution withreplacement solvent leaves the column at the product outlet 408 in thecolumn bottom 404.

Since dispersions readily form films and coagulum, the trays requirefrequent cleaning. For this purpose, each tray 402 in the known columnis assigned a manhole 409 having a diameter of 500 mm and at least onecleaning port 410, the cleaning port in the present case having adiameter of 200 mm. Through the manhole 409, cleaning operatives areable to clean the associated tray 402 and the wall region of the columnpipe 401 that lies directly above said tray 402 using a high-pressurewater jet. However, this cleaning procedure is very complex and, becauseof the water pressures of 2000 bar or more that are used, is dangerous.Furthermore, cleaning is never perfect since the numerous ports on thepipe, in the present case totaling 108, are dirt traps which arevirtually impossible to clean thoroughly.

In contrast, the stripping pipe of the invention, which is illustratedbelow, has a substantially simpler design and permits rapid and thoroughcleaning.

A first embodiment of the stripping pipe of the invention is shown inFIG. 1. Even in the diagram of FIG. 1, the stripping pipe 100 of theinvention exhibits a substantially simpler design than the conventionalstripping column of FIG. 9. This first variant of the invention is usedin particular to treat relatively small batches of product. In thecolumn pipe 101, a total of 18 trays 102 having a diameter of 800 mm arearranged. The column top 103 is widened to a diameter of 1800 mm andserves as a separator for entrained droplets of product. The column topalso houses the product inlet 105, which in the example depicted emergestangentially about midway up the vertical extent of the column top. Atangential feed of this kind prevents excessive foaming when, forexample, dispersions are being fed in. The polymer solution ordispersion fed in flows downward in the column pipe 101 through thetrays 102, while steam fed in in countercurrent in the extended columnbottom 104 by way of an entry port 106 is passed upward. Steam andentrained residual volatiles leave the column at the column top 103 viaan exit port 107 which is subject to subatmospheric pressure. Thestripped dispersion or the polymer solution freed from the organicsolvent leaves the stripping pipe 100 by way of one or more productoutlets 108 provided laterally at the column bottom.

In contrast to the prior art, the column pipe 101 of the stripping pipeof the invention is composed of a plurality—in the example of FIG. 1, atotal of three—pipe sections 101 a, 101 b and 101 c. In the presentcase, the three pipe sections have the same internal diameter.

Groups of six trays 102 are brought together to form inserts 111 a, 111b and 111 c. In contrast to the prior art stripping columns, the trays102 are not fixed to the column pipe but instead are designed asremovable inserts. In the example depicted, precisely one insert 111 aor 111 b or 111 c, respectively, is assigned to each pipe section 101a-10 c. The individual pipe sections are connected to one another, tothe column top 103 and the column bottom 104, respectively, by means offlange connections 112 a-112 d.

One possible design of an insert, and the arrangement of the inserts inthe column pipe 101, are now explained in more detail with reference toFIG. 2, which depicts an enlarged cutaway of the stripping pipe of FIG.1. FIG. 2 shows the bottommost pipe section 101 c with the insert 111 carranged in it. For clarity, the middle region of the pipe section 101 cwith the three further trays of the insert 111 c is not depicted. Thetrays 102 of the insert 111 c are welded together with six elongatemetal plates 113, arranged at the external periphery of the trays, toform the insert. Arranged at the top end of the insert 111 c arecross-struts 114 which run together in an adapter 115. The adapter 115is designed such that it is able to cooperate with automatic liftingtongs, which are not shown here but are introduced into the column pipe101 from above.

In the example depicted, the individual inserts are stacked atop oneanother. In FIG. 2 it can be seen that the bottommost insert 111 c sitson the support port 116 which is welded to the inside of the extendedbottom 104. The total length of the insert corresponds essentially tothe length of the associated pipe section. The overlying insert 111 b issituated on the bottommost insert 111 c; in the embodiment depicted,rods provided on the lower face of the insert 111 b engage incorresponding centering recesses on the top face of the insert 111 c.The inserts themselves are not connected to the column pipe 101. Forintroducing and removing the inserts, the column top 103 is lifted andautomatic lifting tongs engage in the adapter 115 of the topmost insert111 a, which is shaped like the insert 111 c depicted in FIG. 2; thetongs then lift the insert 111 a from the underlying insert 111 b andpull it upward out of the pipe. In the same way, finally, the inserts111 b and 111 c are lifted in succession from the pipe. To aidintroduction and removal, the outer periphery of each insert bears aplurality of sliding elements 117 made of polytetrafluoroethylene(PTFE). There is a generally a certain play between the externalperiphery of the trays 102 and the internal wall of the column pipe 101.Therefore, in order to seal off the resultant space, on the externalperiphery of each tray 102 there is an elastic lip seal 118 which isindicated only in diagrammatic form in FIG. 2 but can be made out moreclearly in the variant depicted in FIG. 5.

In the stripping pipe of the invention, if the trays become soiled, theycan simply be removed and cleaned thoroughly and safely outside thepipe. Accordingly, the column pipe is of very simple design, since thereis no longer any need for manholes for each tray and the numerouscleaning ports. The column pipe has a number of inspection windows 119through which it is possible to monitor the introduction and removal ofthe inserts and, in operation, to monitor any possible clogging of thetrays, and also a number of measuring ports and ports for removingsamples. In total there are only 25 connecting ports. This also makesthe cleaning of the stripping pipe substantially simpler than thecleaning of the stripping columns of the prior art. A further advantageof the simplified constructional design are the lower production costsfor the stripping pipe of the invention.

In the case of three inserts, the total height of the stripping pipe 100of FIG. 1 is about 12 m. The stripping typically takes place attemperatures of from 50 to 90° C. The embodiment depicted is alsosuitable for variants having two or four inserts.

FIG. 3 shows a second embodiment of the stripping pipe of the invention.Components which correspond to those already elucidated in connectionwith FIG. 1, or which fulfill the same function, are labeled with thecorresponding reference numerals raised by 100, and are not elucidatedin any further detail at this point. The column pipe 201 of thestripping pipe 200 of the invention is divided, in the embodiment shown,into four pipe sections 201 a to 201 d, which are flange-connected toone another, each pipe section containing an insert 211 a-d consistingof 6 trays 202. The trays 202 of an insert are at a distance of 400 mmfrom one another. Arranged in the column bottom 204 is a single, firmlyanchored tray 220 which is accessible by way of a manhole 209. Overall,therefore, the stripping pipe 200 has 25 trays 202. Again, the productis supplied by way of an inlet port 205 which opens tangentially intothe column top 203. The product is removed by way of a central port 208at the base of the column bottom 204. Also provided at that point,again, are connections 206 for the introduction of steam, which is takenoff at the column top via the port 207.

In this embodiment, the individual pipe sections have differentdiameters decreasing from top to bottom. In the example depicted, thetopmost pipe section 201 a has a diameter of 1150 mm while thebottommost pipe section 201 d has a diameter of only 1000 mm. Thediameter of the column top 203 is 1800 mm and the total height of thestripping pipe is 16.2 m. Again, inspection windows 219 are provided onthe individual pipe sections.

In one variant (not shown) of the stripping pipe of FIG. 3, four insertseach with six trays are provided, said trays being arranged at adistance of 600 mm and having diameters of from 1600 mm to 1450 mm. Thislarger stripping pipe has an overall height of about 22 m.

In contrast to the variant of FIGS. 1 and 2, the inserts 211 a-211 d inthis second variant lie on step-shaped projections of the flangeconnections 212 a-d, as is clear in particular from the diagram of FIG.4 and the detailed view of FIG. 5, in which the projection formed in theregion of flange 212 b can be seen, the extended topmost tray 202 of theinsert 211 b lying on said projection. For one of the trays 202, FIG. 5also shows in more detail the elastic lip seal 218 at the trayperiphery.

By virtue of the upwardly increasing diameter of the individual pipesections, the individual inserts can easily be removed in successionfrom the column pipe using lifting tongs which engage on the adapter215. Here again, the introduction and removal of the inserts isfacilitated by means of gliding elements 217 which are provided on thelongitudinal profiles 213 and/or cross-profiles 214 which connect thetrays of one insert. In this larger variant of the stripping pipe of theinvention, it is advantageous not to remove the entire column top.Instead, the column top has an opening which can be closed by means of aremovable lid 221 and through which the inserts can be removed.

In the exemplary embodiments of FIGS. 1 to 5 so far, the trays have beendesigned as so-called dual-flow trays. FIG. 6 now shows a variant inwhich a stripping pipe of the invention is provided with cross-flowtrays 302. In the cutaway of the stripping pipe that is depicted, acolumn section 301 can be seen between two connecting flanges 312 a and312 b. The column section 301 accommodates an insert consisting of aplurality of cross-flow trays 302 connected to one another. In theexample depicted, the trays 302 are connected to one another by threadedrods 324 a fixed by a locknut at the ends. The insert is stabilized, inaddition, by means of support rings 325 a running round it. An overflowshaft 322 connects each pair of cross-flow trays 302 lying one above theother. The shaft 322 opens into a pot 323 arranged on the lower tray.

FIG. 6 shows a further variant of the arrangement of an insertconsisting of two or more trays in the associated column section: thesupport ring 325 a of the insert is clamped in the flange connection 312a of two column sections. It can be seen that the upper insert does notlie directly on the lower insert held together by the rods 324 b and thesupport ring 325 b. This variant is particularly suitable for very smallcolumns where the flange connections between the column sections can beundone quickly and the insert can be lifted from the column section. Inthis case too, cleaning is substantially easier than in the case ofknown stripping columns, since here again a complete insert, typicallywith six trays, can be removed in one go from the pipe.

The basic design of dual-flow and cross-flow trays is depicted in FIGS.7 and 8.

FIG. 7 shows a plan view of a dual-flow tray 202 which can be used inthe apparatus of the invention. Approximately 16% of the total area ofthe tray is formed by about 600 holes 226 having an average diameter offrom 10 to 50 mm.

For comparison, FIG. 8 shows the plan view of a cross-flow tray 326which in its middle region possesses numerous holes 306 whose diameteris smaller than that of the holes of a dual-flow tray and is typicallyfrom 2 to 10 mm. A considerable part of the surface of the tray isaccounted for by the downcomer shaft 322, which connects the tray 302with a tray lying below it, and by a pot 323 into which the downcomershaft of the upper tray emerges, as is evident more precisely, inparticular, from the lengthwise section of FIG. 6. It can be seen thatthe specific throughput of such a tray is lower than that of a dual-flowtray, since in the case of the cross-flow tray the area through whichgas is able to flow is lower on account of the areas occupied by theshaft and pot. Consequently, dual-flow trays are generally preferred foruse in the apparatus of the invention.

The invention is elucidated in more detail by the following examples.

EXAMPLE 1

A variant of the apparatus of FIG. 1 consisted of a separator having adiameter of 1400 mm onto which two tube sections, 2800 and 3260 mm longrespectively, with a nominal diameter of 500 mm had been flanged. Twoinserts were installed, with five and six cross-flow trays respectively,each of which trays was at a distance of 400 mm from its neighbor. Theshafts were pipes having nominal diameters of 100 mm, which projected100 mm upward from the respective tray and extended down by 50 mm on thetray below.

These cross-flow trays were fed from the top with 2.0 t/h of an aqueouscosmetic dispersion (50 mPas) and from the bottom with 0.4 t/h of steamat 54° C. (0.15 bar) in the separator present. The intention was todeplete around 600 ppm of t-butanol from the entering dispersion. In thedispersion discharged from the countercurrent stripping pipe of theinvention, t-butanol could no longer be detected by means ofconventional GC analysis with a detection limit of below 10 ppm. Thedepletion was therefore complete.

EXAMPLE 2

In a variant of Example 1, two inserts comprising five and six dual-flowtrays respectively, each of which trays were at a distance of 400 mmfrom its neighbor, were installed. The trays each had 103 holes with adiameter of 20 mm, which corresponded to a free hole area of 16% of thepipe cross section. The dual-flow trays were fed from the top with 3.5t/h of dispersion and from the bottom with 0.7 t/h of steam. Here again,600 ppm of t-butanol were likewise depleted to less than 10 ppm.

Consequently, a column stripping process is provided for even very smalldispersion batches (in this case 6000 kg) which exhibits an efficiencysimilar to that of the large deodorizing columns used to date.

EXAMPLE 3

The apparatus of the invention is also suitable for separating thesolvent from polymer solutions, i.e., for replacing it by water.

Using the apparatus of Example 1, a solution polymer in isopropanol(3270 kg of polymer, 2080 kg of isopropanol, 460 kg of water) as fedinto the separator instead of the dispersion with a throughput of 1680kg/h together with 200 kg/h of steam and was stripped with 500 kg/h ofsteam which was passed in at the column bottom. Following discharge fromthe column bottom, the stripped solution polymer contained only 650 ppmof isopropanol.

EXAMPLE 4

Using the apparatus of Example 2, the isopropanol was stripped frompolymer solution fed in at 2100 kg/h, using 700 kg/h of steam, to alevel of 300 ppm.

1. A countercurrent stripping pipe for removing volatile organicconstituents from reaction products, comprising: a column pipe composedof a plurality of pipe sections connected to one another by flangeconnections, in which pipe sections trays are arranged, a plurality ofsuccessive trays being connected to one another to form at least twoseparate inserts which can be removed from the column pipe; firstconnections for supplying and removing the reaction products; and secondconnections for supplying and removing at least one stripping agent incountercurrent to the reaction products, wherein internal diameters ofsuccessive pipe sections decrease from top to bottom and a removableinsert is arranged in each pipe section.
 2. A countercurrent strippingpipe as claimed in claim 1, wherein up to 10 inserts are arranged in thecolumn pipe.
 3. A countercurrent stripping pipe as claimed in claim 2,wherein each insert has from 3 to 10 trays.
 4. A countercurrentstripping pipe as claimed in claim 2, wherein each insert has from 4 to7 trays.
 5. A countercurrent stripping pipe as claimed in claim 2,wherein each insert has 6 trays.
 6. A countercurrent stripping pipe asclaimed in claim 1, wherein a diameter of the trays of one insertcorresponds substantially to an internal diameter of the column pipe. 7.A countercurrent stripping pipe as claimed in claim 6, wherein thediameter of the trays of the one insert is from 100 to 2500 mm.
 8. Acountercurrent stripping pipe as claimed in claim 6, wherein thediameter of the trays of the one insert is from 500 to 1600 mm.
 9. Acountercurrent stripping pipe as claimed in claim 6, wherein a distancebetween successive trays in an insert is from 200 to 1000 mm.
 10. Acountercurrent stripping pipe as claimed in claim 6, wherein a distancebetween successive trays in an insert is from 400 to 600 mm.
 11. Acountercurrent stripping pipe as claimed in claim 1, further comprisinga widened column top configured to be removable.
 12. A countercurrentstripping pipe as claimed in claim 1, further comprising a widenedcolumn top including an aperture which can be closed and whose diameteris configured to permit removal of the inserts.
 13. A countercurrentstripping pipe as claimed in claim 1, wherein the inserts stand on topof one another in the column pipe.
 14. A countercurrent stripping pipefor removing volatile organic constituents from reaction products,comprising: a column pipe composed of a plurality of pipe sectionsconnected to one another by flange connections, in which pipe sectionstrays are arranged, a plurality of successive trays being connected toone another to form at least two separate inserts which can be removedfrom the column pipe; first connections for supplying and removing thereaction products; and second connections for supplying and removing atleast one stripping agent in countercurrent to the reaction products,wherein internal diameters of successive pipe sections decrease from topto bottom and a removable insert is arranged in each pipe section, andthe inserts lie on steplike connecting regions between each pair ofsuccessive pipe sections.
 15. A countercurrent stripping pipe as claimedin claim 14, wherein up to 10 inserts are arranged in the column pipe.16. A countercurrent stripping pipe as claimed in claim 15, wherein eachinsert has from 3 to 10 trays.
 17. A countercurrent stripping pipe asclaimed in claim 15, wherein each insert has from 4 to 7 trays.
 18. Acountercurrent stripping pipe as claimed in claim 14, wherein eachinsert has 6 trays.
 19. A countercurrent stripping pipe as claimed inclaim 14, wherein a diameter of the trays of one insert correspondssubstantially to an internal diameter of the column pipe.
 20. Acountercurrent stripping pipe as claimed in claim 19, wherein thediameter of the trays of the one insert is from 100 to 2500 mm.
 21. Acountercurrent stripping pipe as claimed in claim 19, wherein thediameter of the trays of the one insert is from 500 to 1600 mm.
 22. Acountercurrent stripping pipe as claimed in claim 19, wherein a distancebetween successive trays in an insert is from 200 to 1000 mm.
 23. Acountercurrent stripping pipe as claimed in claim 19, wherein a distancebetween successive trays in an insert is from 400 to 600 mm.
 24. Acountercurrent stripping pipe as claimed in claim 14, further comprisinga widened column top configured to be removable.
 25. A countercurrentstripping pipe as claimed in claim 14, further comprising a widenedcolumn top including an aperture which can be closed and whose diameteris configured to permit removal of the inserts.
 26. A countercurrentstripping pipe as claimed in claim 14, wherein the inserts stand on topof one another in the column pipe.
 27. A method of removing volatileorganic constituents from polymeric products, comprising: feeding apolymeric product containing volatile organic constituents into thecountercurrent stripping pipe as claimed in claim 1 under conditions toremove volatile organic constituents from the polymeric product.
 28. Amethod of removing volatile organic constituents from polymericproducts, comprising: feeding a polymeric product containing volatileorganic constituents into the countercurrent stripping pipe as claimedin claim 14 under conditions to remove volatile organic constituentsfrom the polymeric product.
 29. A method of replacing an organic solventof a polymer solution with water, comprising: feeding a polymer solutioncontaining an organic solvent into the countercurrent stripping pipe asclaimed in claim 1 under conditions to replace the organic solvent withwater.
 30. A method of replacing an organic solvent of a polymersolution with water, comprising: feeding a polymer solution containingan organic solvent into the countercurrent stripping pipe as claimed inclaim 14 under conditions to replace the organic solvent with water.